For silver halide color photographic materials, the process for forming a color image by using the reactions of dye-forming couplers that can form yellow, magenta, and cyan with a color-developing agent is currently put to practical use widely.
In recent years, improvements in dye-forming couplers for silver halide color photographic materials have been studied diligently in order to improve color reproduction and fastness of images, but there are restrictions on color-developing agents and it is no yet considered that satisfactory improvements have been made. Particularly with respect to cyan couplers, although phenol couplers and naphthol couplers are conventionally used all the time, dyes produced from these couplers have undesirable absorption in the blue and green regions, which is a hindrance to the improvement in color reproduction. molecular extinction coefficient of the cyan dyes that are produced is low is disadvantageous in view of the improvement of sharpness of images.
Recently, cyan dye-forming couplers having new skeletons with a nitrogen-containing heterocyclic ring are studied actively, and a variety of heterocyclic compounds have been suggested. For example, JP-A ("JP-A" means unexamined published Japanese patent application) No. 226,653/1988 describes diphenylimidazole couplers and JP-A Nos. 199352/1988, 250649/1988, 250650/1988, 554/1989, 555/1989, 105250/1989, and 105251/1989 disclose pyrazoloazole couplers. These couplers are described as improved in color reproduction and are characterized in that the absorption characteristics of the dyes produced therefrom are excellent.
However, the dyes produced from the above couplers have defects that the absorption wave form is biased to the short wave side, the fastness to light and heat is poor, and the coupling activity of the couplers themselves is low, which is a serious problem from the practical point of view.
On the other hand, as dye-forming couplers related to the present invention, 2,4-diarylpyrrole couplers are disclosed in U.S. Pat. No. 2,396,396; but since these couplers react with the oxidized product of a developing agent in such a state that the hydrogen in the 1-position of the pyrrole is not dissociated, there are such problems that the coupling activity is low and stain occurs with time after the development processing, and therefore they have not been practically used.